U.S. patent application number 15/429850 was filed with the patent office on 2017-08-17 for catalyst and method for preparing catalyst.
The applicant listed for this patent is HYUNDAI MOTOR COMPANY, KIA MOTORS CORPORATION, POSTECH ACADEMY-INDUSTRY FOUNDATION. Invention is credited to Suk Bong HONG, Donghui JO, Chang Hwan KIM, Pyung Soon KIM, In-Sik NAM, Gi Tae PARK, Taekyung RYU.
Application Number | 20170232428 15/429850 |
Document ID | / |
Family ID | 57821830 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170232428 |
Kind Code |
A1 |
HONG; Suk Bong ; et
al. |
August 17, 2017 |
CATALYST AND METHOD FOR PREPARING CATALYST
Abstract
A catalyst includes LTA zeolite including copper ions, wherein a
Si/Al ratio of the LTA zeolite is 2 to 50. The catalyst is coated
on a honeycomb carrier or a filter. The catalyst removes NOx from a
reaction gas at 100.degree. C. or above. The catalyst has an NOx
conversion rate of 80% at 450.degree. C. or above.
Inventors: |
HONG; Suk Bong; (Pohang-si,
KR) ; JO; Donghui; (Gongju-si, KR) ; RYU;
Taekyung; (Jung-gu, KR) ; PARK; Gi Tae;
(Suseong-gu, KR) ; NAM; In-Sik; (Pohang-si,
KR) ; KIM; Pyung Soon; (Suwon-si, KR) ; KIM;
Chang Hwan; (Seongnam-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HYUNDAI MOTOR COMPANY
KIA MOTORS CORPORATION
POSTECH ACADEMY-INDUSTRY FOUNDATION |
Seoul
Seoul
Pohang-si |
|
KR
KR
KR |
|
|
Family ID: |
57821830 |
Appl. No.: |
15/429850 |
Filed: |
February 10, 2017 |
Current U.S.
Class: |
502/74 |
Current CPC
Class: |
B01D 53/9413 20130101;
B01D 2255/50 20130101; B01J 2229/183 20130101; B01D 2255/915
20130101; C01B 39/14 20130101; B01D 2251/2067 20130101; B01J
2229/186 20130101; B01J 37/0201 20130101; F01N 3/2066 20130101;
B01D 2255/20761 20130101; B01J 29/7607 20130101; F01N 2370/04
20130101; B01J 35/04 20130101; B01D 2255/30 20130101; C01B 39/145
20130101; B01D 53/9418 20130101; B01J 29/072 20130101; B01D
2255/2092 20130101; B01J 2229/34 20130101; B01J 29/80 20130101;
B01J 37/04 20130101; C01B 39/026 20130101; B01J 35/0006 20130101;
B01J 2229/36 20130101; B01J 37/30 20130101; F01N 2570/14 20130101;
B01J 37/08 20130101; B01J 29/763 20130101; B01J 37/0246
20130101 |
International
Class: |
B01J 29/76 20060101
B01J029/76; B01J 35/00 20060101 B01J035/00; B01J 35/04 20060101
B01J035/04; F01N 3/20 20060101 F01N003/20; B01J 37/04 20060101
B01J037/04; B01J 37/08 20060101 B01J037/08; B01D 53/94 20060101
B01D053/94; B01J 29/072 20060101 B01J029/072; B01J 37/30 20060101
B01J037/30 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2016 |
KR |
10-2016-0016512 |
Dec 7, 2016 |
KR |
10-2016-0165932 |
Claims
1. A catalyst comprising linde type A (LTA) zeolite including
copper ions, wherein a silicon/aluminum (Si/Al) ratio of the LTA
zeolite is 2 to 50.
2. The catalyst of claim 1, wherein the catalyst is coated on a
honeycomb carrier or a filter.
3. The catalyst of claim 1, wherein the catalyst removes NOx from a
reaction gas at 100.degree. C. or above.
4. The catalyst of claim 1, wherein the catalyst has an NOx
conversion rate of 80% at 450.degree. C. or above.
5. The catalyst of claim 1, wherein a content of copper in the
catalyst is 1 wt % to 5 wt %.
6. The catalyst of claim 1, wherein the catalyst further comprises
an additive.
7. The catalyst of claim 6, wherein the additive is an alkali metal
or an alkali earth metal, and a ratio of the additive to aluminum
is 0.1 to 0.3.
8. The catalyst of claim 6, wherein the additive is selected from
the group consisting of La, Ce, Zr, Sc, and In, and wherein the
ratio of the additive to aluminum is 0.01 to 0.05.
9. The catalyst of claim 1, further comprising a copper type of
SSZ-13 zeolite.
10. The catalyst of claim 9, wherein a mixing ratio of the LTA
zeolite to the copper-type SSZ-13 zeolite is 1:3 to 3:1.
11. A catalyst comprising LTA zeolite that contains Fe ions,
wherein an Si/Al ratio of the LTA zeolite is 2 to 50.
12. The catalyst of claim 11, wherein the catalyst is coated on a
honeycomb carrier or a filter.
13. The catalyst of claim 11, wherein the catalyst removes NOx from
a reaction gas at 100.degree. C. or above.
14. The catalyst of claim 11, wherein a content of iron in the
catalyst is 1 wt % to 5 wt %.
15. A method for manufacturing a catalyst, comprising steps of:
preparing a LTA zeolite of which a Si/Al ratio is 2 or more;
preparing LTA zeolite containing ions by using the LTA zeolite; and
preparing a copper-type of LTA zeolite by performing copper ion
exchange on the ion-containing LTA zeolite.
16. The method of claim 15, wherein a Si/Al ratio of the LTA
zeolite is 2 to 50.
17. The method of claim 15, wherein the step of preparing the
ion-containing LTA zeolite comprises substituting ions in the LTA
zeolite.
18. The method of claim 15, wherein the step of preparing the
ion-containing LTA zeolite comprises adding the LTA zeolite to an
ammonium salt for reaction and then drying the LTA zeolite, and
wherein the ammonium salt is ammonium nitrate
(NH.sub.4NO.sub.3).
19. The method of claim 15, wherein the step of performing copper
ion exchanging on the ion-containing LTA zeolite comprises adding
the ion-containing LTA zeolite to a copper precursor solution and
stirring the solution.
20. The method of claim 15, further comprising thermally treating
the copper type of LTA zeolite after the preparing of the
copper-type LTA zeolite, wherein the thermal treatment is performed
at a temperature ranging from 1 to 30.degree. C./min from 400 to
750.degree. C.
21. The method of claim 15, wherein the step of preparing the LTA
zeolite having the Si/Al ratio of 2 or more comprises preparing the
LTA zeolite using an LTA seed.
22. A method for manufacturing a catalyst, comprising steps of:
preparing an LTA zeolite of which a Si/Al ratio is 2 or more;
preparing an LTA zeolite containing ions using the LTA zeolite; and
preparing an iron type of LTA zeolite by performing iron (Fe) ion
exchange on the ion-containing LTA zeolite.
23. The method of claim 22, wherein the step of preparing the Fe
ion exchange on the ion-containing LTA zeolite comprises adding the
ion-containing LTA zeolite to an iron precursor solution and
stirring the solution.
24. The method of claim 22, wherein the step of preparing the
ion-containing LTA zeolite comprises adding the LTA zeolite to an
ammonium salt for reaction and then drying the LTA zeolite, and
wherein the ammonium salt is ammonium nitrate
(NH.sub.4NO.sub.3).
25. The method of claim 22, wherein the step of performing the Fe
ion exchange on the ion-containing LTA zeolite further comprises:
mixing the ion-containing LTA zeolite with at least one of
iron(III) nitrate nonahydrate (Fe(NO.sub.3).sub.3.9H.sub.2O),
sulfuric acid hydrate (FeSO.sub.4.7H.sub.2O), iron(II) oxalate
dihydrate (FeC.sub.2O.sub.4.2H.sub.2O), and iron(III) chloride
tetrahydrate (FeCl.sub.2.4H.sub.2O); and stirring the mixture.
26. The method of claim 22, further comprising thermally treating
the Fe-type of LTA zeolite the performing of the Fe ion exchange on
the ion-containing LTA zeolite, wherein the thermal treatment is
performed at a temperature ranging from 1 to 30.degree. C./min from
400 to 750.degree. C.
27. The method of claim 22, wherein the step of preparing the LTA
zeolite having the Si/Al ratio of 2 or more comprises preparing a
LTA zeolite using an LTA seed.
28. The method of claim 22, wherein the step of preparing the LTA
zeolite having the Si/Al ratio of 2 or more comprises preparing a
LTA zeolite without an LTA seed.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority to Korean
Patent Application Nos. 10-2016-0016512 and 10-2016-0165932 filed
in the Korean Intellectual Property Office on Feb. 12, 2016 and
Dec. 7, 2016, the entire contents of which are incorporated herein
by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to a method for manufacturing
a zeolite catalyst. More particularly, the present disclosure
relates to a method for manufacturing a zeolite catalyst of which
high-temperature performance can be improved.
BACKGROUND
[0003] In general, carbon monoxide, hydrocarbons, and nitrogen
oxides are included as harmful materials in exhaust gas of diesel
vehicles. Nitrogen oxides cause environmental problems such as
photochemical smog and acid rain, as well as human diseases.
Therefore, there is a demand for improving engines and developing a
post-treatment technology of exhaust gas.
[0004] The most effective technology for removing nitrogen oxides
uses a selective catalytic reduction (SCR) method. This method has
been developed according to a reducing agent such as ammonia (NH3),
urea, hydrocarbon (HC), and the like, and various catalysts.
Ammonia (NH.sub.3) has been known to be effective in removing
nitrogen oxides from a fixed object such as a power plant and an
incinerator. Since there is a problem of storage/transport and use
of ammonia, in case of a moving object such as a vehicle, urea has
been known to be effective as it is capable of being easily
decomposed to ammonia by heat decomposition and a hydration
reaction.
[0005] As the catalyst for use in the selective catalyst reduction
method, zeolite-based catalysts such as copper (Cu)/zeolite having
excellent functions has been developed.
[0006] In particular, high temperature activity of such a catalyst
is important in treatment of high-temperature exhaust gas.
[0007] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention, and therefore, it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY
[0008] The present disclosure has been made in an effort to provide
a method for manufacturing a zeolite catalyst of which
high-temperature performance can be improved.
[0009] A catalyst according to an exemplary embodiment of the
present disclosure includes linde type A (LTA) zeolite including
copper ions, wherein an Si/Al ratio of the LTA zeolite is 2 to
50.
[0010] The catalyst may be coated on a honeycomb carrier or a
filter.
[0011] The catalyst may remove NOx from a reaction gas at
100.degree. C. or above.
[0012] The catalyst may have an NOx conversion rate of 80% at
450.degree. C. or above.
[0013] A content of copper in the catalyst may be 1 wt % to 5 wt
%.
[0014] The catalyst may further include an additive.
[0015] The additive may be an alkali metal or an alkali earth
metal, and a ratio of the additive and aluminum may be 0.1 to
0.3.
[0016] The additive may be selected from a group consisting of La,
Ce, Zr, Sc, and In, and the ratio of the additive and aluminum may
be 0.01 to 0.05.
[0017] The catalyst may further include a copper type of SSZ-13
zeolite.
[0018] A mixing ratio of the LTA zeolite and the copper-type SSZ-13
zeolite may be 1:3 to 3:1.
[0019] According to another exemplary embodiment, a catalyst
includes LTA zeolite that contains Fe ions, wherein an Si/Al ratio
of the LTA zeolite is 2 to 50.
[0020] The catalyst may be coated on a honeycomb carrier or a
filter.
[0021] The catalyst may remove NOx from a reaction gas at
100.degree. C. or above.
[0022] A content of iron in the catalyst may be 1 wt % to 5 wt
%.
[0023] Accordig to another exemplary embodiment of the present
disclosure, a method for manufacturing a catalyst includes:
preparing a LTA zeolite of which a Si/Al ratio is 2 or more;
preparing s LTA zeolite containing ions by using the LTA zeolite;
and preparing a copper-type of LTA zeolite by performing copper ion
exchange on the ion-containing LTA zeolite.
[0024] A Si/Al ratio of the LTA zeolite may be 2 to 50.
[0025] The preparing of the ion-containing LTA zeolite may include
substituting ions in the LTA zeolite.
[0026] The preparing of the ion-containing LTA zeolite may include
adding the LTA zeolite to an ammonium salt for reaction and then
drying the LTA zeolite, wherein the ammonium salt may be ammonium
nitrate (NH.sub.4NO.sub.3).
[0027] The performing of copper ion exchanging on the
ion-containing LTA zeolite may include adding the ion-containing
LTA zeolite to a copper precursor solution and stirring the
solution.
[0028] The method for manufacturing the catalyst may further
include thermally treating the copper type of LTA zeolite after the
preparing of the copper-type LTA zeolite, wherein the thermal
treatment may be performed at a temperature ranging from 1 to
30.degree. C./min from 400 to 750.degree. C.
[0029] The preparing of the LTA zeolite having the Si/Al ratio of 2
or more may include preparing the LTA zeolite using an LTA seed or
not using an LTA seed.
[0030] According to another exemplary embodiment of the present
disclosure, a method for manufacturing a catalyst includes:
preparing an LTA zeolite of which a Si/Al ratio is 2 or more;
preparing an LTA zeolite containing ions using the LTA zeolite; and
preparing an iron type of LTA zeolite by performing iron (Fe) ion
exchange on the ion-containing LTA zeolite.
[0031] The preparing of the Fe ion exchange on the ion-containing
LTA zeolite may include adding the ion-containing LTA zeolite to an
iron precursor solution and stirring the solution.
[0032] The preparing of the ion-containing LTA zeolite may include
adding the LTA zeolite to an ammonium salt for reaction and then
drying the LTA zeolite, wherein the ammonium salt may be ammonium
nitrate (NH.sub.4NO.sub.3).
[0033] The performing of the Fe ion exchange on the ion-containing
LTA zeolite may further include: mixing the ion-containing LTA
zeolite with at least one of iron(III) nitrate nonahydrate
(Fe(NO.sub.3).sub.3.9H.sub.2O), sulfuric acid hydrate
(FeSO.sub.4.7H.sub.2O), iron(II) oxalate dihydrate
(FeC.sub.2O.sub.4.2H.sub.2O), and iron(III) chloride tetrahydrate
(FeCl.sub.2.4H.sub.2O); and stirring the mixture.
[0034] The method for manufacturing the catalyst may further
include thermally treating the Fe-type of LTA zeolite the
performing of the Fe ion exchange on the ion-containing LTA
zeolite, wherein the thermal treatment may be performed at a
temperature ranging from 1 to 30.degree. C./min from 400 to
750.degree. C.
[0035] The preparing of the LTA zeolite having the Si/Al ratio of 2
or more may include preparing a LTA zeolite using an LTA seed or
not using an LTA seed.
[0036] As described, according to the method for manufacturing the
zeolite catalyst according to the exemplary embodiment, acidity is
low and thus the high-temperature performance of the catalyst can
be improved while reducing the consumption of urea.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 illustrates a structure of an LTA zeolite according
to an exemplary embodiment of the present disclosure.
[0038] FIG. 2 is a graph illustrating a measurement result of
removal of nitrogen oxide of a zeolite catalyst in various
temperature ranges according to an exemplary embodiment of the
present disclosure and a comparative example of the present
disclosure.
[0039] FIG. 3A is a measurement result of an NOx conversion ratio
in a fresh state, and FIG. 3B is a measurement result of the NOx
conversion ratio after performing hydro-thermal aging at 75.degree.
C.
[0040] FIG. 4 shows a NOx conversion ratio of a catalyst according
to Experimental Example 3.
[0041] FIG. 5 to FIG. 7 show a NOx conversion ratio of a catalyst
according to Experimental Example 4.
[0042] FIG. 8 and FIG. 9 show a NOx conversion ratio of a catalyst
according to Experimental Example 5.
[0043] FIG. 10 to FIG. 13 show a NOx conversion ratio of a catalyst
according to Experimental Example 6.
[0044] FIG. 14 to FIG. 17 show a NOx conversion ratio of a catalyst
according to Experimental Example 7.
[0045] FIG. 18 to FIG. 21 show a NOx conversion ratio of a catalyst
according to Comparative Example 1.
[0046] FIG. 22 shows a NOx conversion ratio of a catalyst according
to Comparative Example 1.
[0047] FIG. 23 is a block diagram of an exhaust gas purification
device that employs the zeolite catalyst according to an exemplary
embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0048] The present disclosure will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments are shown. As those skilled in the art would
realize, the described embodiments may be modified in various
different ways, all without departing from the spirit or scope of
the present disclosure.
[0049] The drawings and description are to be regarded as
illustrative in nature and not restrictive, and like reference
numerals designate like elements throughout the specification.
[0050] In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements.
[0051] Hereinafter, a method for manufacturing a catalyst according
to an exemplary embodiment of the present disclosure will be
described in detail. A catalyst manufactured in the present
exemplary embodiment may be a zeolite catalyst.
[0052] A method for preparing zeolite for manufacturing the
catalyst according to an exemplary embodiment of the present
disclosure will be described.
[0053] First, LTA zeolite is prepared. In preparation of the LTA
zeolite, a seed may or may not be used. A Si/Al ratio of the LTA
zeolite prepared in the present stage may exceed 1. More
specifically, the Si/Al ratio may be 2 to 50. Preferably, the Si/Al
ratio may be 5 to 30. More preferably, the Si/Al ratio may be 8 or
more.
[0054] As an example, a process for preparing the LTA zeolite using
the seed will be described.
[0055] In order to prepare the LTA zeolite, an LTA seed is mixed in
a mixture of aluminum hydroxide (Al(OH).sub.3) and tetraethyl
orthosilicate (Si(OC.sub.2H.sub.5).sub.4).
[0056] Specifically, a 1,2-dimethyl-3-(4-methylbenzyl)imidazolium
hydroxide aqueous solution and aluminum hydroxide (Al(OH).sub.3)
are mixed and the mixture is primarily stirred, and then
tetramethylammonium hydroxide pentahydrate is additionally mixed
and then secondarily stirred so as to prepare a first mixture.
[0057] Here, with respect to the total weight of the first mixture,
20 to 35 wt % of 1,2-dimethyl-3-(4-methylbenzyl)imidazolium
hydroxide, 1 to 2 wt % of aluminum hydroxide (Al(OH).sub.3), 1 to 5
wt % of tetramethylammonium hydroxide pentahydrate, and a residual
quantity of water are mixed, and the primary stirring and the
secondary stirring may be respectively performed for about 0.5 to
1.5 h.
[0058] Tetraethyl orthosilicate (TEOS) (Si(OC.sub.2H.sub.5).sub.4)
is mixed into the first mixture and then third stirring is
performed, and then the LTA seed is mixed and fourth stirring is
performed so as to prepare a second mixture.
[0059] 30 to 35 wt % of TEOS may be mixed with respect to the total
weight of the second mixture, and the amount of LTA seed may be 2
to 6 wt % with respect to the total weight of the entire silicon
included in the LTA zeolite.
[0060] In addition, the third stirring may be performed for about 2
to 4 h, and the fourth stirring may be performed for about 20 to 28
h.
[0061] Next, the second mixture is sufficiently heated to cause
hydrolysis of the TEOS, and ethanol and water generated from the
hydrolysis of TEOS are evaporated such that a third mixture is
prepared.
[0062] The second mixture may be heated at a temperature between
70.degree. C. and 90.degree. C.
[0063] Next, a hydrofluoric aqueous solution is mixed in the third
mixture, and a fourth mixture is prepared through heating,
cleansing, and drying processes.
[0064] Here, the third mixture may be heated for a constant time
period at a temperature of about 150.degree. C. to 200.degree. C.,
the cleansing process may be iteratively performed, and the drying
process may be performed at room temperature.
[0065] Next, heat treatment is additionally performed to remove an
organic material from the fourth mixture such that the LTA zeolite
for manufacturing the zeolite catalyst according to an exemplary
embodiment of the present disclosure is manufactured.
[0066] The heat treatment may be performed at a temperature between
500.degree. C. and 700.degree. C. for about 6 to 10 h, and a Si/Al
ratio of the LTA zeolite may be 2 to 50 in the present exemplary
embodiment.
[0067] When the LTA zeolite is prepared without using the seed, the
LTA zeolite can be prepared as follows. As organic
structure-inducing molecules, 0.0 mol to 0.2 mol of aluminum
hydroxide and 0.0 mol to 0.2 mol of tetramethylammonium hydroxide
(hereinafter referred to as TMAOH) are added in 0.1 mol to 1.0 mole
of 1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxide
(hereinafter referred to as 12DM3 (4MB)IOH) in a plastic beaker and
then sufficiently stirred. Next, tetraethyl orthosilicate
(hereinafter referred to as TEOS) is added to the reactants in a
proportion of 1 mol, and the mixture is sufficiently stirred.
[0068] Next, the solution is sufficiently heated at 60.degree. C.
to 100.degree. C. until the amount of ethanol generated due to
hydrolysis of TEOS added to the solution is completely removed, and
at the same time the amount of water is 0 to 10 mol. Then, when 0.1
to 1.0 mol of hydrogen fluoride (HF) is added and sufficiently
mixed, a reaction mixture having Chemical Formula 1 is
obtained.
1 SiO.sub.2:0.0-0.2 Al(OH).sub.3:0.0-0.2 TMAOH:0.1-1.0 R:0.1-1.0
HF:0-10 H.sub.2O [Chemical Formula 1]
[0069] wherein R denotes 12DM3 (4MB)IOH.
[0070] The reaction mixture is then moved to a Teflon reactor, and
placed in a container that is made of stainless steel again and
heated at 100.degree. C. to 200.degree. C. for 0.1 to 14 d to
prepare the LTA zeolite. The LTA zeolite prepared by the above
method may also have a Si/Al ratio of 2 to 50. However, the
above-described manufacturing method is illustrative and is not
limited to as above-described.
[0071] An XRD pattern of the LTA zeolite manufactured in the
present stage is shown in the lower part of FIG. 1. A structure of
the LTA zeolite manufactured in the present stage is shown in the
upper part of FIG. 1.
[0072] Next, a step of preparing LTA zeolite containing ions using
the manufactured LTA zeolite will be described in detail.
[0073] First, LTA zeolite is placed into an ammonium salt,
refluxed, washed, and dried to manufacture an NH.sub.4-type LTA
zeolite containing NH.sub.4+ions.
[0074] Here, the ammonium salt may be ammonium nitrate
(NH.sub.4NO.sub.3).
[0075] The reflux process can be carried out at a temperature of 60
to 100.degree. C. for 5 to 7 h.
[0076] In the present embodiment, ammonium ions are exemplarily
described as the ions, but the present disclosure is not limited
thereto. That is, use of other ions and ion salts is also included
within the scope of this disclosure.
[0077] Then, LTA zeolite including ions undergoes copper (Cu) ion
exchange such that a Cu type of LTA zeolite including copper ions
is prepared.
[0078] For the copper ion exchange, the LTA zeolite ions is
injected into a copper precursor solution such as copper acetate
monohydrate, copper nitride, copper nitrate, copper sulfate, and
the like, and stirred, and then cleansing and drying processes are
performed such that the Cu type of LTA zeolite can be prepared.
[0079] As a possible alternative, the LTA zeolite including ions
may undergoes iron (Fe) ion exchange such that a Fe type of LTA
zeolite including Fe ions can be prepared in another exemplary
embodiment of the present disclosure.
[0080] The performing of the Fe ion exchange can be carried out by
mixing the LTA zeolite including ions with at least one of
iron(III) nitrate nonahydrate (Fe(NO.sub.3).sub.3.9H.sub.2O),
sulfuric acid hydrate (FeSO.sub.4.7H.sub.2O), iron(II) oxalate
dihydrate (FeC.sub.2O.sub.4.2H.sub.2O), and iron(III) chloride
tetrahydrate (FeCl.sub.2.4H.sub.2O) and stirring.
[0081] Next, the Cu type of LTA zeolite or the Fe type of LTE
zeolite is heated in an oven with a gradually increasing
temperature, and then a heat treatment process is performed such
that the zeolite catalyst according to an exemplary embodiment of
the present disclosure is manufactured.
[0082] Here, for the heat temperature of the Cu type of LTA zeolite
or the Fe type of LTE zeolite, the temperature may be increased to
400 to 750.degree. C. at a rate of 1 to 30.degree. C./min, and then
the heat treatment may be performed to about 1 to 24 h.
[0083] Hereinafter, experimental examples of the present disclosure
will be described. However, the following experimental examples are
only exemplaries, and the present disclosure is not limited to the
following experimental examples.
EXPERIMENTAL EXAMPLE
LTA Zeolite Catalyst Preparation
1 LTA Zeolite Preparation
[0084] In a plastic beaker, with respect to the total weight of an
aqueous solution, 29.4 wt % (12.38 g) of
1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxide aqueous
solution and 0.1733 g of aluminum hydroxide were mixed and then
stirred for about 1 h, and then tetramethylammonium hydroxide
pentahydrate at 0.4152 g was additionally mixed therein and then
stirred for about 1 h.
[0085] Next, tetraethyl orthosilicate (TEOS) at 6.80 g was mixed
therein and then stirred for about 3 h, 4 wt % of LTA seed with
respect to the entire silica injected thereto was added thereto and
then stirred for about 24 h, and the mixture was heated at
80.degree. C. to cause hydrolysis of the TEOS such that 5.90 g of
ethanol and 5.37 g of water generated from the hydrolysis were
evaporated.
[0086] Next, with respect to the total weight of the aqueous
solution, 48 wt % (0.577 ml) of a hydrofluoric aqueous solution was
mixed therein.
[0087] Then, the mixture to which the hydrofluoric aqueous solution
was added was injected into a steel container and then heated at
175.degree. C. for about 17 h while rotating the container at a
speed of 60 rpm such that a solid product was generated, and the
solid product was iteratively cleansed and then dried at room
temperature.
[0088] In order to remove an organic material from the dried
mixture, the dried mixture was heat-treated at 600.degree. C. in a
muffle furnace for about 8 h to thereby manufacture an LTA zeolite,
XRD analysis was performed on the manufactured zeolite to determine
that the zeolite had an LTA structure, and a Si/Al ratio was
determined to be 16 through ICP analysis.
2. Zeolite Catalyst Preparation
[0089] 2 g of the manufactured LTA zeolite and 100 ml of 1 M
ammonium nitrate were mixed in a two-neck flask, and the mixture
was refluxed at 80.degree. C. for about 6 h.
[0090] Next, the mixture was iteratively cleansed with a filter and
distilled water and then dried at room temperature, and the
cleansing and drying processes were repeated two times such that an
NH.sub.4 type of LTA zeolite was manufactured.
[0091] The dried NH.sub.4 type of LTA zeolite was injected into 100
ml of a 0.01 M copper acetate monohydrate (Cu(OAc).sub.2.H.sub.2O)
solution and then stirred at room temperature for about 6 h.
[0092] The dried NH.sub.4 type of LTA zeolite was injected into 100
ml of a 0.01 M copper acetate monohydrate (Cu(OAc).sub.2.H.sub.2O)
solution and then stirred at room temperature for about 6 h.
[0093] In order to determine a removal rate of nitrogen oxide in
the zeolite catalyst according to an exemplary embodiment of the
present disclosure, an experiment was performed to measure a
removal rate of the nitrogen oxide by temperature, and a result of
the experiment is shown in FIG. 2.
[0094] FIG. 2 is a graph illustrating a result of an experiment
performed to measure a removal rate of nitrogen oxide in the
zeolite catalyst according to an exemplary embodiment of the
present disclosure and in a zeolite catalyst according to a
comparative example in various temperature ranges.
[0095] In FIG. 2, the horizontal axis denotes a temperature
(.degree. C.) and the horizontal axis denotes a removal rate (%) of
nitrogen oxide.
[0096] As the zeolite catalyst according to a comparative example,
Cu/SSZ-13 (Si/Al=13) was used.
[0097] In order to determine high-temperature performance of the
zeolite catalyst according to an exemplary embodiment of the
present disclosure, two zeolite catalysts, one with no treatment
(Exemplary Embodiment 1) and the other one having undergone heat
treatment at 750.degree. C. for about 24 h with air containing 10%
humidity (Exemplary Example 2), were respectively used in
experiments.
[0098] In addition, in order to determine high-temperature
performance of Cu/SSZ-13, two catalysts, one with no treatment
(Comparative Example 1) and the other one having undergone heat
treatment at 750.degree. C. for about 24 h with air containing 10%
humidity (Comparative Example 2), were respectively used in
experiments.
[0099] In order to determine a removal rate by temperature, the
zeolite catalysts of the exemplary embodiments and the comparative
examples were supplied with 500 ppm of nitride oxide (NO), 500 ppm
of ammonia (NH.sub.3), 5% of oxygen, and humidity of 10% at a gas
hourly space velocity (GHSV) of nitrogen (N.sub.2) of 100,000, and
a removal rate of nitrogen oxide was measured while changing the
temperature between 150.degree. C. and 550.degree. C.
[0100] First, referring to FIG. 2, the nitrogen oxide removal rate
of Exemplary Embodiment 1 is similar to that of Comparative Example
1 until the temperature reaches 400.degree. C., but when the
temperature exceeds 400.degree. C., the nitrogen oxide removal rate
of Exemplary Embodiment 1 is excellent compared to Comparative
Example 1.
[0101] In addition, in Exemplary Embodiment 2, the nitrogen oxide
removal rate was about 30% better than Comparative Example 2 from a
zone where the temperature exceeds 300.degree. C.
[0102] Hereinafter, a catalyst according to an exemplary embodiment
will be described. A catalyst according to the present exemplary
embodiment includes LTA zeolite that contains copper ions, and a
Si/Al ratio of the LTA zeolite may be 2 to 50. The catalyst may be
coated on a honeycomb carrier or a filter.
[0103] In the catalyst according to the present exemplary
embodiment, a Si/Al ratio of the LTA zeolite may be 2 to 50. When
the Si/Al ratio is less than 2, the hydrothermal stability may be
poor, and when the Si/Al ratio is 50 or more, there may be a
problem of low performance because there are few aluminum sites
that may contain Cu or Fe.
[0104] The catalyst can be manufactured by a manufacturing method
according to the present exemplary embodiment. The catalyst can
remove NOx from a reaction gas at a temperature of 100.degree. C.
or more.
[0105] In addition, as shown in FIG. 1, the catalyst according to
the present exemplary embodiment may have a NOx conversion ratio of
above 80% at a temperature above 450.degree. C.
[0106] In the catalyst, a copper/aluminum ratio may be 0.1 to 0.6.
Alternatively, an amount of copper in the catalyst may be 1 wt % to
5 wt %. When the copper content is set to 2 wt % in a catalyst
having a Si/Al ratio of 23, even when hydrothermal aging is
performed at a high temperature of 900.degree. C. or more for 24 h,
excellent NOx purification efficiency is exhibited. In the present
disclosure, the term hydrothermal means a process to send a flow of
air of relative humidity 10% at a predetermined temperature and
time.
[0107] In addition, in the exemplary embodiment, the catalyst may
further include an additive. The additive may include an alkali
metal or an alkaline earth metal. Alternatively, the additive may
be selected from a group consisting of La, Ce, Zr, Sc, and In, and
in this case, catalyst performance at low temperatures can be
improved.
[0108] When the additive is an alkali metal or alkaline earth
metal, the ratio of additive/aluminum may range from 0.1 to 0.3.
When the additive is one or more selected from the group consisting
of La, Ce, Zr, Sc, and In, the ratio of additive/aluminum may range
from 0.01 to 0.05.
[0109] In addition, the catalyst according to an embodiment of the
present disclosure may be a mixture of copper-type LTA zeolite and
copper-type SSZ-132 zeolite. In this case, a mixing ratio of the
copper-type LTA zeolite to the copper-type SSZ-13 zeolite may be
1:3 to 3:1. The mixing ratio of the copper-type LTA zeolite to the
copper-type SSZ-13 zeolite may be 1:1. When the copper type LTA
zeolite and the copper type SSZ-13 are mixed and used, a NOx
purification rate at a low temperature can be improved.
[0110] As described above, the LTA zeolite catalyst according to
the present disclosure has a Si/Al ratio of 2 to 50. Depending on a
freshness state or a hydrothermal aging temperature and time, the
Si/Al ratio that indicates optimum performance may be varied.
[0111] The effect of the LTA zeolite catalyst according to the
various exemplary embodiments of the present disclosure will now be
described with reference to the following experimental
examples.
EXPERIMENTAL EXAMPLE 2
Measurement of NOx Conversion Rate
[0112] NOx conversion rates of copper-type LTA zeolite
(.box-solid.) having a Si/Al ratio of 11, copper-type LTA zeolite (
) having a Si/Al ratio of 16, and copper-type SSZ-13 zeolite
(.tangle-solidup.) having a Si/Al ratio of 16 according to
temperature were respectively measured, and the measurement results
are shown in FIG. 3. FIG. 3(a) shows a measurement result of the
NOx conversion rate in a fresh state, and FIG. 3 shows a
measurement result of the NOx conversion rate after performing
hydrothermal aging at 750.degree. C.
[0113] In this case, the conversion rate was measured under the
same conditions as Experimental Example 1. That is, the catalyst
was supplied with 500 ppm of nitride oxide (NO), 500 ppm of ammonia
(NH.sub.3), 5% of oxygen, and humidity of 10% at a gas hourly space
velocity (GHSV) of nitrogen (N.sub.2) of 100,000, and a removal
rate of nitrogen oxide was measured while changing the temperature
between 150.degree. C. and 550.degree. C. This is the same in other
experimental examples below.
[0114] Referring to FIG. 3(a) and (b), the LTA catalyst according
to the present disclosure had an excellent NOx conversion rate
before hydrothermal aging, and the NOx conversion rate was
remarkably improved even at a high temperature after hydrothermal
aging at 750.degree. C.
EXPERIMENTAL EXAMPLE 3
LTA Zeolite Catalyst Having Copper Content of 2 wt % and Si/Al
Ratio of 23
[0115] In LTA zeolite having a Si/Al ratio of 23, manufactured
according to the present disclosure, a copper content in copper ion
exchange was set to 2 wt %. With respect to such a catalyst,
hydrothermal aging was carried out at various temperature and time
conditions, and NOx conversion performance was measured and
measurement results are shown in FIG. 4. Referring to FIG. 4, it
was determined that even when hydrothermal aging was performed for
24 h at 900.degree. C., excellent NOx conversion performance was
maintained at 50% or more.
EXPERIMENTAL EXAMPLE 4
Catalyst Including Additive
[0116] In LTA zeolite having a Si/Al ratio of 16, manufactured
according to the present disclosure, NOx conversion rates were
measured while various additives were added, and measurement
results are shown in FIG. 5 to FIG. 7. FIG. 5 shows a result of
adding an alkali metal or an alkaline earth metal as an additive,
FIG. 6 shows a result of adding a La-based metal as an additive,
and FIG. 7 shows a result of adding Zr, Sc, and In as an additive.
Referring to FIG. 5 to FIG. 7, it was determined that, when various
additives are added, NOx conversion performance at a low
temperature was improved without significantly affecting the NOx
conversion performed at a high temperature.
EXPERIMENTAL EXAMPLE 5
Mixed with Cooper-Type of SSZ-13 Zeolite
[0117] A catalyst was prepared by varying a mixing ratio of the LTA
zeolite having a Si/Al ratio of 16, manufactured according to the
present disclosure and a copper-type SSZ-13 zeolite, and NOx
conversion performance according to temperature was measured and
measurement results are shown in FIG. 8 and FIG. 9. FIG. 8 shows a
measurement result of NOx conversion performance in a fresh state,
and FIG. 9 shows a measurement result of NOx conversion performance
after hydrothermal aging at 900.degree. C. for 12 h.
[0118] Referring to FIG. 8 and FIG. 9, performance was excellent as
the content of copper-type of SSZ-13 zeolite was high in the case
of the fresh catalyst, and performance was excellent as the content
of the copper-type of zeolite was high. When all the results shown
in FIG. 8 and FIG. 9 are taken into account, it can be determined
that the performance was excellent in the case where the mixing
ratio of copper-type LTA zeolite to copper-type SSZ-13 zeolite was
1:1 to 3:1.
EXPERIMENTAL EXAMPLE 6
Experiment with Different Si/A Ratios
[0119] A NOx conversion rate according to temperature was measured
by varying a Si/Al ratio of the LTA zeolite catalyst according to
the present disclosure. The NOx conversion was measured by varying
the aging temperature of the catalyst in a fresh state, to
750.degree. C., 850.degree. C., and 900.degree. C., respectively,
and measurement results are shown in FIGS. 10 to 13. FIG. 10 shows
performance at the fresh state, FIG. 11 shows performance at the
state of aging at 750.degree. C., FIG. 12 shows performance at the
state of aging at 850.degree. C., and FIG. 13 shows performance at
900.degree. C. In FIG. 10 to FIG. 13, a content of copper was set
to make a Cu/Al ratio become 0.5.
[0120] Referring to FIG. 10 to FIG. 13, it could be determined that
the ratio of Si/Al, which shows optimum activity depending on aging
temperature, was different for each catalyst. Therefore, a person
skilled in the art can appropriately use the Si/Al ratio optimum
for the conditions of use of the catalyst.
EXPERIMENTAL EXAMPLE 7
Experiment with Different Si/Al Ratios
[0121] The experiment was performed using a method that is similar
to Experimental Example 6, except that a reaction temperature was
consistent, and NOx conversion rates according to a Si/Al ratio of
a catalyst are shown in FIG. 14 to FIG. 17. FIG. 14 shows
performance at a fresh state, FIG. 15 shows performance in a state
of aging at 750.degree. C., FIG. 16 shows performance in a state of
aging at 850.degree. C., and FIG. 17 shows performance in a state
of aging at 900.degree. C.
[0122] As a result, the performance was excellent when the Si/Al
ratio was low at a low temperature in the case of the fresh
catalyst, but the performance was excellent when the Si/Al ratio
was high at a high temperature.
[0123] In addition, referring to FIG. 15 to FIG. 17, in the aging
state, the performance was excellent when the Si/Al ratio was 10 to
30.
COMPARATIVE EXAMPLE 1
Experiment with Different Si/Al Ratios with Respect to Cu-type of
SSZ-13 Catalyst
[0124] Comparative Example 1 is similar to Experimental Example 7,
except that rather than the LTA zeolite of the present disclosure,
SSZ-13 zeolite was used, and NOx conversion rates according to
Si/Al ratios at each temperature were measured and measurement
results are shown in FIG. 18 to FIG. 21. FIG. 18 shows performance
in a fresh state, FIG. 19 shows performance in a state of aging at
750.degree. C., FIG. 20 shows performance in a state of aging at
850.degree. C., and FIG. 21 shows performance in a state of aging
at 900.degree. C.
[0125] In comparison between the measurement results of Comparative
Example 1 shown in FIG. 18 to FIG. 21 and the measurement results
of Experimental Example 7 shown in FIG. 14 to FIG. 17, the result
of Comparative Example 1 shows that high-temperature performance at
500.degree. C. was relatively low compared to that of the LTA
zeolite according to the present disclosure. In addition, in
comparison with the results of Comparative Example 1, shown in FIG.
20 and FIG. 21 and the results of Exemplary Embodiment 7 shown in
FIG. 16 and FIG. 17, performance was significantly different after
aging at 850.degree. C. or above. That is, compared to the SSZ-13
catalyst, the LTA zeolite catalyst according to the exemplary
embodiment of the present disclosure shows a remarkably improved
effect even when the Si/Al ratio is the same as that of the SSZ-13
catalyst.
[0126] In addition, a catalyst according to another exemplary
embodiment includes LTA zeolite that contains Fe ions, and a Si/Al
ratio of the LTA zeolite may be 2 to 50. The catalyst may be coated
on a honeycomb carrier or a filter, and the catalyst can remove NOx
from a reaction gas at 100.degree. C. or above. The catalyst may
include ions at a content of 1 wt % to 5 wt %.
EXPERIMENTAL EXAMPLE 8
LTA Zeolite Catalyst Containing Fe
[0127] LTA zeolite having a Si/Al ratio of 16 according to the
present disclosure was prepared. In this case, Fe ions were added
to the LTA zeolite such that an Fe-type of LTA zeolite having an
Fe/Al ratio of 0.2 was prepared. In addition, as a comparative
example, SSZ-13 zeolite containing Fe ions was prepared.
[0128] With respect to the Fe-type of LTA zeolite catalyst
(exemplary embodiment) and the Fe-type of SSZ-13 zeolite catalyst,
NOx conversion rates with respect to each temperature were measured
and measurement results are shown in FIG. 22. The conversion rate
of each catalyst in a fresh state and the conversion rate after
hydrothermal aging at 850.degree. C. were measured.
[0129] Referring to FIG. 22, it could be determined that the
Fe-type of LTA zeolite catalyst according to the present disclosure
has remarkably improved performance after hydrothermal aging at
850.degree. C. compared to the Fe-type of SSZ-13 zeolite
catalyst.
[0130] Hereinafter, an example of application of the zeolite
catalyst manufactured according to the method for manufacturing the
zeolite catalyst according to an exemplary embodiment of the
present disclosure will be described with reference to FIG. 23.
[0131] FIG. 23 is a block diagram of an exhaust gas purification
device to which the zeolite catalyst according to an exemplary
embodiment of the present disclosure is applied.
[0132] As shown in FIG. 23, an exhaust gas generated from an engine
10 sequentially passes a turbocharger 20, a diesel oxidation
catalyst (DOC) device 30, a catalyzed particulate filter (CPF) 40,
a spray nozzle 50, and a selective catalytic reduction (SCR) device
60 such that harmful materials in the exhaust gas are removed.
Here, the turbocharger 20, the DOC device 30, the CPF 40, the spray
nozzle 50, and the SCR device 60 may be installed in an exhaust
pipe 70.
[0133] The engine 10 includes a plurality of cylinders (not shown)
for combustion of an air mixture. The cylinder is connected with an
intake manifold (not shown) to receive the air mixture, and the
intake manifold is connected with an intake pipe (not shown) to
receive external air.
[0134] Further, the cylinder is connected with an exhaust manifold
(not shown) such that exhaust gas generated during a combustion
process is collected in the exhaust manifold. The exhaust manifold
is connected with the exhaust pipe 70.
[0135] The turbocharger 20 rotates a turbine (not shown) using
energy of the exhaust gas so as to increase the air intake
amount.
[0136] The DOC device 30 may be provided in a rear end of the
turbocharger 20. In the DOC device 30, HC and CO are oxidized and
NO is oxidized to NO.sub.2. In addition, in order to effectively
generate NO.sub.2, at least one of the zeolite catalyst, which has
ion-exchanged with a transition metal and is manufactured according
to the above-described method of the present disclosure and a noble
metal may be included in the DOC device 30, and the zeolite
catalyst manufactured according to the above-described method of
the present disclosure may be used as a supporter of a cold start
catalyst (CSC) that intercalates NOx generated at initial
cold-starting in the DOC device 30.
[0137] The CPF 40 is provided in a rear end of the DOC device 30,
and includes a catalyst filter CPF.
[0138] The CPF 40 collects particulate matter (PM) in the exhaust
gas and regenerates the collected PM (i.e., soot). The regeneration
of soot is performed when a pressure difference between an inlet
and an outlet of the CPF 40 is higher than a predetermined
pressure.
[0139] The spray nozzle 50 is provided between the CPF 40 and the
SCR device 60, and sprays a reducing agent to exhaust oxidized in
the DOC device 30 and the CPF 40. The reducing agent may be
ammonia, and generally urea is sprayed from the spray nozzle 50 and
the sprayed urea is decomposed to ammonia.
[0140] The exhaust gas mixed with the reducing agent and NO.sub.2
generated from the DPC device 30 is supplied to the SCR device
60.
[0141] The SCR device 60 is provided in a rear end of the spray
nozzle 50, and includes the zeolite catalyst ion-exchanged with the
transition metal, manufactured according to the above-described
method of the present disclosure. The LTA zeolite catalysts
according to various exemplary embodiments described above may be
included in the SCR device 60. A detailed description of the same
components will be omitted. The SCR device 60 reduces NO in the
exhaust gas to nitrogen gas N.sub.2 using NO.sub.2 generated from
the DOC device 30 and the reducing agent such that NO.sub.x in the
exhaust gas can be reduced.
[0142] Further, the Cu type of LTA zeolite catalyst according to
the exemplary embodiment of the present disclosure, which can be
applied to the DOC device 30 and the SCR device 60, may be solely
used or mixed with a Cu type of SSZ-13 catalyst. When the Cu type
of SSZ-13 catalyst and the Cu type of LTA zeolite catalyst
according to the exemplary embodiment of the present disclosure are
mixed, low-temperature performance and high-temperature performance
can be more improved.
[0143] As described, according to the method for manufacturing the
zeolite catalyst according to the exemplary embodiment of the
present disclosure, acidity is low and thus the high-temperature
performance of the catalyst can be improved while reducing the
consumption of urea.
[0144] While this invention has been described in connection with
what is presently considered to be practical example embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *